1. Field of the Invention
An aspect of this disclosure relates to a printer.
2. Description of the Related Art
Printers for printing receipts are widely used, for example, for cash registers in shops and stores, and for automated teller machines (ATM) and cash dispensers (CD) in banks. Generally, in such a printer for printing receipts, thermal paper used as recording paper is conveyed into a space between a thermal head and a platen roller, and information is printed by the thermal head at a predetermined position on the recording paper.
This type of printer is configured such that the platen roller is detachable to easily place recording paper between the thermal head and the platen roller.
In a typical printer for printing information on recording paper with a thermal head, the thermal head is pressed toward a platen roller to improve the contact between the thermal head and the platen roller during printing.
Japanese Patent No. 3734753 discloses a configuration of a thermal printer including a biasing part that is provided on a lock arm and applies a biasing force to a platen roller to press the circumferential surface of the platen roller against a line thermal head, an operation part formed on the lock arm, a pressing part that engages the operation part and presses down the operation part in opposition to the biasing force of the biasing part, and a platen roller detaching part that disengages a rotational shaft of the platen roller from a rotational shaft support part of the lock arm.
Japanese Laid-Open Patent Publication No. 2000-318260 discloses a configuration where a frame includes a slit having a shape for guiding a bearing of a platen roller, and the bearing of the platen roller is pressed against the slit by a lock arm to support the platen roller. The lock arm uses a biasing force of a pressure spring for pressing a thermal head against the platen roller. The pressure spring biases a head support for supporting the thermal head in a direction to move away from the lock arm.
Japanese Laid-Open Patent Publication No. 2008-068551 discloses a thermal printer including a first spring that is disposed between a lock arm and a thermal head and biases a platen roller toward the thermal head, and a second spring that is disposed between the thermal head and a body frame and biases the thermal head in a direction to bring the thermal head into close contact with the platen roller.
Japanese Laid-Open Patent Publication No. 2000-094767 discloses a thermal printer where a thermal head and a platen are provided as a unit. The platen is movable away from the thermal head. When the platen is moved away from the thermal head, a paper passage is formed between the thermal head and the platen. When paper is set in the thermal printer, the paper is put through the paper passage.
With the related-art technologies, however, a biasing part such as a coil spring is provided on a back support plate of a lock arm to press a thermal head toward a platen roller relative to the back support plate of the lock arm. This configuration poses some problems.